1. Technical Field
The present invention is directed toward a key lock, and more particularly toward a key lock having a removable plug.
2. Background Art
Key locks with removable plugs are old in the art, and generally involve a shell mounted to the object to be locked, a plug insertable into and removable from the shell; and two keys, one of which allows the plug to be removed from the shell.
U.S. Pat. No. 4,398,405 discloses a key controlled lock with removable plug in which a retaining end of a control tumbler prevents withdrawal of the plug by extending into a circumferential groove within the barrel. The plug becomes removable when a separate key retracts the control tumbler into the plug, and extends another end of the control tumbler from the plug into an aligned longitudinal groove to allow removal of the plug. Only the biased retaining end of a control tumbler holds the plug within the barrel. Because tumblers are generally made of a lightweight material not designed to withstand the longitudinal forces of one pulling a plug out of the shell while the retaining end of the control tumbler extends into the retaining groove, the thin retaining end of the tumbler does not necessarily provide the strength required to prevent a person from breaking off or bending the control tumbler when attempting to forcibly remove such a plug.
Another structure is shown in U.S. Pat. No. 4,630,457. However, while this structure allows the use of a relatively stronger flange on the plug near the key face to retain the plug in the shell, this structure prevents a full 360.degree. rotation of the plug within the barrel and therefore prevents it from being used in some environments which require such a full range of operation.
The present invention is directed toward overcoming one or more of the problems set forth above.